Sensing rotation and linear acceleration, in such applications as automotive control systems, etc., has typically required the pairing of distinct gyroscopes and accelerometers. Both bulk and ring resonators, suitably designed and configured, may serve as inertial sensors of rotation and of translational acceleration. For example, a bulk acoustic wave (BAW) gyroscope may be driven to resonate in one or more bulk modes by a set of drive electrodes such that a change in the bulk mode shape may be sensed to derive rotation of the sensor. Recent work has shown that the self-same resonator mass that constitutes a gyroscope, as just described, may also be excited to move in a translational mode and may serve as an accelerometer, sensing acceleration along one-, two- or three-orthogonal axes. The resonator mass may thus be excited to operate in either a gyroscope mode, a linear sensing mode, or in a combined mode, wherein distinct modes are excited simultaneously by distinct drive electrodes and detected by distinct sensing electrodes.
Sonmezoglu et al., “Simultaneous detection of linear and Coriolis accelerations on a mode-matched MEMS gyroscope,” IEEE Int. Conf. on MEMS, pp. 32-35, (26-30 Jan. 2014), incorporated herein by reference, describe a signal processing modality applied to a tuning-fork gyroscope in which residual quadrature signals on differential sense-mode electrodes are used to measure linear acceleration action on the sense axis of the gyroscope. The effect of linear acceleration along that gyroscope axis can then be compensated to suppress its effect on gyroscope output.
It would be desirable, however, for there to be a method or apparatus whereby linear acceleration within a plane might be sensed without the need for a distinct excitation signal for sensing the mode of the resonator, thereby reducing size, power requirements and cost of a sensor that provides both gyroscopic and linear acceleration data.